Interventional radiology concept and classification Interventional radiology was introduced to China in the early 1980s and has rapidly developed into an emerging edge discipline integrating medical imaging and clinical treatment, involving the diagnosis and treatment of many systems such as digestive, respiratory, orthopedic, urological, neurological, and cardiovascular diseases. In particular, interventions have opened up new treatment pathways for conditions that were previously considered incurable or difficult to treat (various cancers, cardiovascular diseases), and are simple, safe, less invasive, less comorbid, and more effective. It is a “non-surgical” method of diagnosing and treating various diseases by percutaneous puncture and cannulation under the guidance of imaging methods, such as drug infusion, vascular embolization or dilation and angioplasty. Because of its unique features in disease diagnosis and treatment (minimally invasive, reproducible, accurate positioning, high efficacy, fast results, low complication rate, easy application of multiple techniques) that traditional internal and external medicine does not have, it has rapidly established its important position in the field of modern medical diagnosis and treatment. In November 1996, the State Science Committee, the Ministry of Health and the State Administration of Medicine jointly held the “Seminar on Strategic Issues of Interventional Medicine in China”, which officially listed interventional medicine as the third major treatment discipline alongside with medical and surgical therapies, and called it Interventional Medicine. It is foreseeable that with the continuous development of interventional medicine, this discipline will be subdivided into neurointerventional, cardiac interventional, gastrointestinal interventional, etc., just like the clinical disciplines of internal medicine and surgery. The development and popularity of interventional radiology has given patients more opportunities for rehabilitation, and it has become the preferred method of elective treatment, which is much more concerned and welcomed by patients. I. Basic concept of interventional radiology Interventional radiology is based on diagnostic imaging, under the guidance of medical imaging diagnostic equipment, the use of puncture needles, catheters and other interventional devices, the treatment of disease or the collection of histological, bacteriological and physiological, biochemical data for diagnosis. A brief history of the development of interventional radiology In 1953, Dr. Sven-Ivar Seldinger of Sweden pioneered the method of percutaneous femoral artery cannulation with trocar needles, guide wires and catheters for angiography, which laid the foundation for contemporary interventional radiology. 1964, American radiologist Dotter developed the use of coaxial catheter system for angioplasty, based on which balloon catheters and metal stents were introduced. The concept of Interventional diagnostic radiology was first introduced by Margtlis in 1967 in the AJR journal, and in 1973 Gruntzig invented the double-lumen balloon catheter for coronary artery dilation, and in 1976 Wallanee systematically described interventional radiology and formed a consensus. In 1976, Wallanee systematically described interventional radiology and formed a consensus. Classification of interventional radiology (a) According to the classification of interventional radiology methods: 1, puncture / drainage: such as cysts, hematomas, substantial organ puncture treatment; blocking the destruction of nerve conduction for pain relief. 2, Perfusion/embolization: such as treatment of bleeding from various causes; treatment of parenchymal organ tumors; elimination or reduction of organ function, such as splenic artery embolization for hypersplenism. 3.Plasty: can restore the lumen organ morphology, such as arterial stenosis; establish new channels, such as TIPSS; eliminate abnormal channels, such as occlusion of tracheoesophageal fistula. 4.Other: such as removal of intravascular foreign body, gallbladder lithotripsy, etc. (II) Classification according to treatment areas: 1. Interventional radiology of the vascular system (1) Lesions of the blood vessels themselves, using angioplasty and perfusion to treat stenosis, vascular malformations, arteriovenous fistulas and bleeding from ruptured blood vessels. (2) Treatment of neoplastic diseases using perfusion embolization. (3) Elimination of organ function using arterial embolization, such as splenic embolism. (4) Angiography and invasive imaging diagnosis by combining angiography with other imaging devices. (2) Interventional radiology of non-vascular system (1) Treatment of stenosis caused by various reasons using angioplasty, such as esophageal stenosis and airway stenosis. (2) Treatment of cysts, abscesses, hematomas, effusions and obstructive jaundice, hydronephrosis, etc. using puncture and drainage (3) Use puncture to collect tissue and make pathological specimens (4) Use of puncture to treat tumors or pain by injecting drugs or applying physical or chemical factors through puncture needles. Transcatheter arterial embolization (TAE) is an important basic technique of interventional radiology, which can be defined as the technique of injecting or delivering an embolic substance into the target vessel through a catheter under X-ray television fluoroscopy to occlude it to achieve the desired therapeutic purpose. The mechanism is to block the target vessel to cause ischemic necrosis of the tumor or target organ; to block or destroy the abnormal vascular bed, lumen and channel to normalize the hemodynamics; to block the vessel to decrease the distal pressure or to seal the ruptured vessel directly from the vessel to facilitate hemostasis. From the pharmacokinetic characteristics, briefly explain the principle that intra-arterial catheter administration can increase the concentration of drugs in target organs: pharmacokinetics is a mathematical model to study the distribution of drugs in the body and other dynamic changes in the law, the drug can have phase I (absorption phase), phase II (equilibrium phase) and phase III (elimination phase) distribution after intravenous injection. The I phase of drug distribution in vivo after intravenous injection is a period of time before the drug distribution reaches equilibrium, and the distribution of drug at this time is determined by the local blood flow, and the local distribution of drug is more when the blood supply to the organ is large. When the drug is injected through the catheter artery, the drug enters the target organ first, and its distribution phase I is different from that of intravenous drug delivery, the distribution of the drug in the target organ is not affected by the blood flow distribution, and it becomes the largest distribution of the drug in the whole body. The distribution phase II, also known as the rapid redistribution phase, occurs several minutes or even hours after drug injection and is influenced by the lipid solubility and protein binding of the drug in addition to the perfusion volume of the organ, and the distribution of the drug in the target organ is also more in this phase than in the intravenous mode of drug administration. The maximum peripheral plasma drug concentration (CMAX) and the area under the plasma drug concentration curve (AUC) are important parameters for pharmacokinetic studies, and a high value will increase the chance of toxic side effects, while a low value will affect the efficacy of the drug. During arterial drug infusion, due to the first-pass metabolism (especially liver) and first-pass extraction of target organs, the maximum peripheral plasma drug concentration and the area under the curve of plasma drug concentration and time are lower than those of intravenous injection, which can improve the efficacy and reduce the toxic side effects of drugs. V. First-pass effect and laminar flow phenomenon in arterial drug perfusion and their significance 1. First-pass effect is the phenomenon that drugs are extracted and metabolized when they pass through the target organ for the first time, and also includes some other effects. Most drugs are metabolized in the liver, and the first-pass effect is evident during intrahepatic arterial drug perfusion. The first-pass effect when the drug is perfused through the artery can achieve the effect of improving the efficacy and reducing the side effects, and certain drugs that are limited in use due to the side effects when administered systemically can be safely used by means of arterial drug delivery. 2, laminar flow phenomenon The specific gravity of drugs is usually smaller than that of blood, when the drug enters the blood vessels and does not mix with blood quickly, especially when administered in the prone position, the drug often flows in the upper layer of the blood column, preferentially entering the ventral opening of the blood vessels to the body or preferentially distributed in the ventral part of the target organ. For example, when administered in the carotid artery, the drug may preferentially enter the ophthalmic artery, causing macular damage, and after entering the intracranial artery the drug is more preferentially distributed to the anterior cerebral artery blood supply area. Mechanism and advantages of local drug infusion for thrombosis: Research and clinical practice prove that fibrinolytic enzyme is a protein hydrolase formed by fibrinolytic zymogen under the action of fibrinogen activator such as streptokinase and urokinase, which can make the insoluble fibrin forming thrombus cleave into soluble fibrin fragments and make the clot be dissolved. The advantages of local perfusion thrombolytic agent: (1) The dosage of local drug perfusion thrombolytic agent is small, only 1/10 to l/4 of the dosage of systemic thrombolytic agent. (2) The efficiency of local perfusion thrombolytic agent is about 79% to 90%, while the efficiency of systemic thrombolytic agent is about 53%. (3) The systemic reaction of local perfusion thrombolysis is small, and there are few serious complications such as bleeding. Percutaneous transluminal angioplasty (PTA) is a method to dilate or recanalize atherosclerotic arteries or other causes of vascular stenosis or occlusive lesions using catheter technology. Because PTA is different from surgical angioplasty, the terms “percutaneous” and “transluminal” are used before angioplasty to distinguish it. PTA includes balloon dilatation angioplasty, endovascular stenting, laser angioplasty, atheromatous resection, ultrasonic angioplasty, etc. Mechanism of balloon angioplasty The “controlled injury” theory is currently accepted as the treatment mechanism of angioplasty, when the balloon is filled, the pressure inside the balloon is transmitted to the vessel wall. Restricted tears in the intima and media of the vessel wall, hyperextension of the media tissue and tearing of the atherosclerotic plaque are the main mechanisms responsible for lumen expansion. Balloon angioplasty, a mechanical treatment for injured vessel wall components, is only partially controllable, but it is not possible to predict the extent and nature of the injury and therefore to estimate the effect of the healing response on the degree of vessel opening after vascular injury. VIII. Mechanism of vascular stent dilatation Whether it is a self-expanding stent or a balloon-expanding stent, balloon dilatation remains the main means to make the lumen of the stenotic vessel dilate, followed by stent support of the dilated vessel, so the lumen opens and blood flow is restored. Two important features of stent placement are: no obstruction of the branch vessel opening and no stimulation of atheromatous plaque formation. However, the stent is a heterologous substance for the blood vessel and stimulates the vessel to cause reactive hyperplasia, making the chance of restenosis still higher. When renal artery stenosis occurs, renal perfusion pressure decreases and renal blood flow decreases, resulting in ischemia of renal tissue (especially renal cortex), which stimulates the glomerular parietal organ to increase the amount of renin secretion and produce angiotensin workers under the action of converting enzymes, which is then converted into angiotensin II with strong smooth muscle contraction by the action of hydrolase, resulting in higher peripheral resistance and higher blood pressure. At the same time, angiotensin II stimulates the adrenal cortex to secrete more aldosterone, which causes sodium and water retention and increases blood volume, leading to a further increase in blood pressure.